Which microorganism is the dominant methane-producing archaeon in the human gut?

Methanobrevibacter smithii is the dominant methane-producing archaeon in the human gut.

Although it is often discussed alongside gut bacteria, M. smithii belongs to the archaea, a separate major branch of life. It is a methanogen: an anaerobic microorganism that produces methane while obtaining energy from hydrogen and carbon dioxide. This activity can alter the chemical environment used by other microbes during digestion.

The species commonly lives in the colon, where it consumes hydrogen released by fermenting bacteria. By removing hydrogen, it can help other microbial reactions proceed more efficiently. Researchers therefore study it as part of the gut microbiome rather than as an isolated pathogen.

M. smithii is not known as a conventional infectious disease agent. Its presence varies among people, and scientists continue investigating links between methanogens, digestion, diet, and metabolic health. A common mix-up is calling it a bacterium: its cell structure and evolutionary history place it among archaea.